The medical examiner's report showed Michael Thompson, 33, died after overdosing on four drugs. Two were opioid painkillers: fentanyl and hydromorphone. He also had lorazepam, a sedative, and amitriptyline, an anti-depressant, in his system.

Two days after Thompson's death, a package of white powder arrived for him in the mail. His father, Tom Thompson, said the envelope came from reChem Labs, a research chemical company.

Michael Thompson died of a drug overdose in March 2015. (CBC)

He and his wife looked up the name of the powder online and said it was an equivalent to Ativan, the brand name for lorazepam.

Thompson took the package to the local RCMP detachment. That triggered a drug trafficking investigation. Police have not named the target of their investigation.

Designer drugs

Officers wrapped up their probe in mid-January and determined there was no basis for drug trafficking charges.

"The investigation determined that the matter was not criminal in nature, so it was concluded," said spokesman Const. Mark Skinner.

In the United States, Drug Enforcement Administration officers say some substances sold as research chemicals are actually designer drugs — drugs tweaked with small chemical changes so they no longer fall under government regulation.

A spokesperson for the U.S. Drug Enforcement Agency has said research chemicals are often deceptively marketed.

ReChem says on its website that its chemicals are for research use and not for human consumption. The company responded to a CBC News request for an interview with an email saying it has never stocked or sold lorazepam. It also said it was working with agencies to determine how its name was linked to a parcel. There was no response to further requests for an interview.

RCMP are not disclosing whether the package sent to Michael Thompson included a designer drug.

"I know you're talking about a broader issue that might be involved, but in this specific case the matter has been concluded. It's been determined the matter is not criminal in nature," said Skinner.